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Maple syrup urine disease (MSUD)

Maple syrup urine disease (MSUD) is a very rare inherited condition.

Babies with MSUD cannot break down certain amino acids. These amino acids then build up in the blood and urine, which can be harmful.

Your baby's urine may smell like maple syrup, which gives the disease its name.

Without treatment, MSUD can cause life-threatening problems within a few days of birth.

These include:

  • fits
  • comas
  • brain damage
  • developmental delay

Babies in Ireland with MSUD

Around 1 in 155,200 babies born in Ireland have MSUD.

One altered gene is inherited from each parent.

How heel prick screening can help

If the heel prick suggests your baby may have MSUD, they will be referred to a specialist.

Your baby will be put on a special diet. This is a protein-restricted diet with supplements of vitamins, amino acids and minerals. As they grow up, your child will need to stick to this diet for life.

Babies treated early should have normal brain development and good health.

Milder forms of MSUD may not be detected by screening, because the condition can start later in life.

Page last reviewed: 12 December 2022
Next review due: 12 December 2025